The present invention relates to a method for writing a servo signal, to be used for placing a head at proper positions on a magnetic disk, to the magnetic disk of a magnetic disk unit.
With the increase of recording density in recent years, the precision of head positioning required of magnetic disk units is increasing rapidly. In order to realize high-precision head positioning, it is essential to reduce synchronous vibration (vibration synchronous with the revolution of the disk) which impairs the positioning accuracy. The main cause of the synchronous vibration is vibration of a servo writer or vibration of the disk during servo write being recorded as variations in the servo pattern. There exists a method for compensating for the synchronous vibration as disclosed in JP-A-9-35225, in which the shape of each track (write error) is learned or measured after the servo pattern recording (servo write) and the head positioning is carried out compensating for the synchronous vibration based on the measurement.